Example and notebook folder

[markus-zimmermann]

Does it make sense to have an example and a notebook folder? Maybe we can have a single folder, although unclear what the name should be. Some notebooks are simple examples, others are not.

[felixlandmeyer]

Keras and scikit-learn call their examples ‘examples’. If we want to add examples as Python scripts at some point, this would be a better solution. Since we only use Jupyter notebooks as examples, 'notebooks' should also fit. I don't mind :)